In this paper we present a system that recovers building facet images from multiple source images and, as a rst step towards detailed analysis of microstructures, extracts windows from walls. The system employs a sophisticated multi-image texture mapping technique to eliminate the corrupting eeects of shadows and occlusions and to nd a \best piece representation" of each facet. The system is model-driven, providing a context-based environment for microstructure analysis. The window extraction module focuses attention on wall facets, attempting to extract the 2-D window patterns attached to the walls using an oriented region growing technique. High-level knowledge is incorporated to simplify the computation of symbolic window extraction. The algorithms are typically useful in urban sites. Experiments show successful applications of this approach to site model reenement.